Manufacture of polyvalent metal soaps



Patented June 25, Hidi MANUFACTURE OF POLYVALENT METAL APS Charles C. Townc, Beacon, N. Y., assignor to The Texas Company, New York, N. Y., a corporation of Delaware No Drawing. Application December 18, 1937, Serial No. 180,557

8 Claims.

This invention relates to the manufacture of ,polyvalentrmetalsoaps, and more particularly polyvalent metal naphthenates from naphthenic acids such as are obtained from petroleum.

One of the principal objects of this invention is to provide a method of manufacturing metallic soaps of this character which is eiiective to secure a substantially increased yield of improved product in a simple and expeditious manner.

Other objects and advantages of the invention will be apparent from the following description and the accompanying claims.

In the manufacture of soaps such as metallic naphthenates of this character, it has heretofore been the practice to efiect double decomposition by the addition to a water solution of an alkali metal naphthenate of a water solution of a polyvalent or heavy metal salt to secureaprecipitation of the polyvalent or heavy metal naphthenatewith concomitant production of a salt of the alkali metal which remains in solution. Considerable difficulty is experienced in the manufacture of certain polyvalent or heavy metal soaps in this manner, due to the fact that extremely low yields are obtained, because the metal salt is unstable in aqueous solution and the double decomposition reaction does not go to completion under these conditions.

I have discovered that unexpectedly large yields are obtained where the polyvalent or heavy metal salt is added in solid form to the alkali metal soap solution as opposed to the customary practice of adding the salt in solution form. This is directly contrary to the result which would be expected from the law of mass action, and is apparently explained by the fact that the added metal of the salt is immediately removed from the scene of reaction by this procedure, whereas in the case where a water solution of the metal salt is employed, secondary reactions or side reactions take place which reduce the quantity of the metal salt available to produce the desired metallic soap.

The present invention is applicable to the manufacture of soaps of such metals as tin, iron, zinc, nickel, chromium, manganese, aluminum, copper, lead, and the like. For purposes of easy description, the expression polyvalent metal is hereinafter used throughout the description and claims to designate metals of this character. As a further advantage of my invention, in addition to the substantially higher yield specified above, it is found that the polyvalent metal soaps produced have a higher metal content indicating a purer product. The present invention appears particularly applicable to the manufacture of such polyvalent metal soaps in which the metal exists in the ous form, such for example as stannous, ferrous, cuprous, mercurous and the like.

Unusually good results have been secured by naphthenate, which is described as a preferred embodiment of the invention. My method comprises neutralizing naphthenic acids with a water solution of an alkali metal base, such as sodium hydroxide, potassium hydroxide, and the like, to form a water solution of the corresponding alkali metal naphthenate. To this solution is then added in solid form sufiicient water soluble polyvalent metal salt, such as stannous chloride, to react with the alkali metal naphthenate to produce a precipitation of polyvalent metal naphthenate while forming a water solution of the alkali metal salt by double decomposition. Thereafter, the precipitate is separated from the water solution. This is effectively accomplished by adding a water immiscible organic solvent in which the precipitated polyvalent metal naphthenate is soluble, and agitating to dissolve the precipitated naphthenate in the solvent. Suitable organic solvents ior this purpose comprise benzol, toluol, naphtha, and the like. The mix is then allowed to stand to stratify into a solvent layer containing the dissolved metal naphthenate and a water solution layer, and the layers are then separated as by decantation. The solvent may then be stripped to recover the metal naphthenate.

By way of example, naphthenic acids of comparatively high molecular weight obtained from heavy residual petroleum oil, were employed, said acids having the following tests:

Neutralization number, 130; Saponification number, 137; Ash, 0.15%; and Non-saponifiable matter, 24.0%

Thirty pounds of the acids were charged in the reaction kettle with 300 pounds of water, and 6.5 pounds of caustic soda solution (48.5%) were added. The water to acid ratio of 10:1 as used above enables the end point of the operation to be more easily recognized, although it is found that this ratio may be reduced to 5: 1 or less without reduction in yield or character of the product. The quantity of sodium hydroxide is calculated to neutralize the naphthenic acids and form a substantially neutral solution of sodium naphthenate. The temperature of the kettle was then brought to 140 F. and 8.7 pounds of solid stannous chloride crystals were added gradually over a period of ten minutes with agitation. The quantity of stannous chloride is calculated to complete the reaction by double decomposition of the sodium naphthenate to stannous naphthenate; but an excess of stannous chloride is avoided, since such an excess results in the formation of tin oxychloride which causes increased diificulty in the clarification of the final product.

this method in the manufacture of stannous By reason of the addition of the stannous chloride in solid form, side reactions which occur with the metal salt in solution, including the production and precipitation of tin oxychloride, are prevented, and substantially all of the tin of the metal salt remains active for reaction with the sodium naphthenate to produce a precipitate of stannous naphthenate.

Following the addition of the solid stannous chloride, 68 pounds of benzol were added at once with continued agitation until the precipitated stannous naphthenate soap had dissolved in the henzol. The mass was then allowed to stand for two hours to stratify into an upper benzene layer and a lower water layer. The water layer was removed and the benzol layer filtered through an inactive clay to clarify the same. The benzol was then stripped off in a vacuum still employing an inert gaseous atmosphere, suflicient vacuum being used so that a maximum stripping temperature of 250 F. was sufiicient to remove the benzol. The stannous naphthenate so obtained was a plastic brown liquid of good character and purity, having the following tests:

Ash per cent 14.73 Theoretical ash based on neutralization 1 number per cent 15.4 Yield as computed by ratio of ash to theoretical ash per cent 96 Insoluble in precipitation naphtha per cent 0.06 Neutralization number In the above example, it is'noted that a yield of 96% of stannous naphthenate based on the calculated theoretical yield from the quantity of naphthenic acids employed was obtained, as compared with yields of the order of about 40% or less when the stannous chloride is added in solution form. While an elevated temperature of the order of about F. was employed in the above example during the precipitation of the stannous soap, it is found that equally good results may be obtained by precipitation of the soap at temperatures varying from normal atmospheric temperatures up to said elevated temperature, It is desirable to maintain temperatures, particularly the temperatures of stripping to remove the benzol, as low as possible in order to preserve the desirable properties and color of the product. For this purpose, a low boiling cutter is employed so that it can be stripped'at a comparatively low temperature, particularly with the aid of vacuum.

While the invention has been particularly described above in connection with the manufacture of polyvalent metal naphthenates, it is to he understood that this invention is also applicable to the manufacture of polyvalent metal soaps of other acids, such as the higher fatty acids, including stearic, oleic', palmitic, etc., and mixtures thereof, and also the substituted fatty acids such as the halogenated fatty acids and the like.

Obviously many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. In the manufacture of a polyvalent metal soap from a water solution of an alkali metal soap, the steps which comprise adding directly to the said water solution a water-soluble polyvalent metal salt, which tends to decompose in water, in solid form unmixed with water to cause a precipitation of polyvalent metal soap, and separating the polyvalent metal soap from the resulting solution.

2. The method in the manufacture of a polyvalent metal naphthenate which comprises neutralizing naphthenic acids with a water solution of an alkali metal base to form a water solution of alkali metal naphthenate, then adding a water soluble polyvalent metal salt, which tends to decompose in water, in solid form unmixed with water to said solution to cause a precipitation of polyvalent metal naphthenate, and separating the polyvalent metal naphthenate from the resulting solution.

3. The method in the manufacture of a polyvalent metal naphthenate in which the polyvalent metal exists in the ous form, which comprises neutralizing naphthenic acids with a water solution of an alkali metal base to form a water solution of alkali metal naphthenate, then adding a water soluble salt of a polyvalent metal in the ous form in solid state unmixed with water to cause a precipitation of polyvalent metal naphthenate in the ous form, adding a water immiscible organic solvent to the resulting mix to dissolve the precipitated naphthenate in the said solvent, allowing the mix to stratify into a solvent layer containing the dissolved naphthenate and a water solution layer, separating the said layers, and stripping the solvent from the solvent layer to obtain the desired polyvalent metal naphthenate.

4. The method in the manufacture of stannous naphthenate which comprises neutralizin naphthenic acids with a water solution of an alkali metal base to form a water solution of alkali metal naphthenate, then adding a water soluble stannous salt in solid form unmixed with water to cause precipitation of stannous naphthenate, and separating the stannous naphthenate from the resulting solution.

5. The method in the manufacture of stannous naphthenate which comprises neutralizing naphthenic acids with a water solution of sodium hydroxide to form a water solution of sodium naphthenate, then adding stannous chloride in solid form unmixed with water to cause a precipitation of stannous naphthenate, adding a water immiscible organic solvent to the resulting mix to dissolve the precipitated stannous naphthenate in the said solvent, allowing the mix to stratify into a solvent layer containing the dis solved stannous naphthenate and a water solution layer, and separating the said layers.

6. In the manufacture of a polyvalent metal naphthenate from a water solution of an alkali metal naphthenate, the steps which comprise adding tothe said water solution a water soluble polyvalent metal salt, which tends to decompose in water, in solid form unmixed with water to cause a precipitation of polyvalent metal naphthenate, and separating the polyvalent metal naphthenate from the resulting solution.

'7. In the manufacture of stannous naphthenate from a water solution of an alkali metal naphthenate, the steps which comprise adding a water soluble stannous salt in solid form unmixed with water to cause a precipitation of stannous naphthenate, and separating the stannous naphthenate from the resulting solution.

8. The method of claim '7 in which the added water soluble stannous salt is stannous chloride.

CHARLES C. TOWNE. 

